1. Field of the Invention
The present invention relates generally to the field of telecommunications devices. More specifically, the present invention is directed to systems and methods for optimizing timing phase in telecommunications equipment.
2. Description of the Related Art
Currently, in the field of analog modem devices, and particularly with respect to the V.92 quick connect phase I, a digital modem transmits quick timing sequence (QTS) signals at the rate of 8000 symbols per second to the analog modem. The QTS signals consist of 128 repetitions of the sequence {+V, +0, +V, −V, −0, −V} where V is defined to be the pulse code modulation (PCM) code word whose Ucode is UQTS and 0 is the PCM code word with Ucode 0[1]. After analog-to-digital conversion of the voice band modem signal and demodulation, the receiver can get a 4 kHz tone. The challenge in this arrangement is to utilize the 4 kHz tone and the converged decision feedback equalizer (DFE) coefficients to lock the timing phase to the optimal point relative to the symbol interval. The desired result is to adjust the timing interpolator to sample the equalized signal at the maximum eye opening instant. It is recognized that this can be achieved at the phase of (2i+1)π/2, where iε{integer} of the 4 kHz tone.
The prior approach to solving this problem was to utilize the precursor equalizer (EQ) output to get accurate timing phase estimation. In order to obtain a valid precursor EQ output for estimation purposes, it was necessary to wait until the precursor EQ delay line is filled with sufficient QTS samples. In order to make the appropriate calculations, it is necessary to fill twice as long as the delay line in order to calculate both sine and cosine of the initial phase respectively. As a result, there is a time cost of 168 QTS symbols in order to make the appropriate phase estimation with this approach.
Although it is possible to achieve the desired result through this solution, the system must be relatively complex and will incur the indicated time delay associated with the stated calculation. In systems of this nature, there is always a need to improve performance by achieving a desired result more quickly or through a less complex calculation. The inventors of the instant application have achieved such a solution which improves performance by achieving the desired result in less time and through utilizing a less complex system and calculation.